Inclusion Criteria:

1. Patients with CML-CP treated for at least two years by Imatinib Mesylate 400 mg / d,

2. Patients in complete cytogenetic response for at least 1 year

3. Patients with residual disease detectable by quantitative RT-PCR (RQ-PCR)

4. ECOG ≤ 2,

5. Age ≥ 18 years

6. Signed informed consent,

7. Membership of a social security system

Exclusion Criteria:

1. Patients with CML-CP Philadelphia chromosome negative diagnosis.

2. Patients previously treated with Imatinib Mesylate at doses above 400 mg / day

3. Patient with non-hematologic toxicity of grade III or IV in Imatinib Mesylate 400mg /
d

4. Patient with a medical condition endocrine, psychiatric, neurological, renal, hepatic
or cardiac progressive uncontrolled by medical treatment

5. Pregnant or breastfeeding women, women of childbearing potential not using a
contraceptive method effective

6. Known HIV positive

7. Patients previously treated with another tyrosine kinase inhibitor

8. Patient participating in another interventional clinical trial

9. History of non-compliance to Imatinib Mesylate